Electronic devices for safety-related tasks require a high level of functional safety, with the term “functionally safe” referring to the term “functional safety as” used in the international publication Draft-IEC 1508.
A key feature of functionally safe electronic devices is that they include special means for avoiding, detecting and handling errors and malfunctions.
A common way to avoid, detect and handle errors and malfunctions is to design multi-channel redundancy-based electronic devices, in which the same operations are carried out in parallel in all the channels. Results and output values are compared to determine whether an error has occurred in one of the channels.
One particular group of errors that is particularly significant, if one is striving to guarantee functionally safe operation, is systematic errors in modules, units or components of channels. Errors of this kind may be caused, for example, by the logic structure, i.e., the way the individual components and modules are interconnected, or by their physical characteristics, which are governed by the manufacturing process used. Extensive certification is required to prove that the application in question is sufficiently free of systematic errors.
Semiconductor technology changes very rapidly nowadays, and manufacturing processes are modified after very short periods of time. As a result, one often has to take repeated action to prove that the components and units in question are free of systematic errors because components and units of this kind must be subjected to extensive certification before they can be used in systems rated functionally safe.
As a result of the rapid innovation cycle in the semiconductor industry, this certification has to be carried out afresh for each new generation of microprocessor or memory chip, for example, with the certification process taking considerable time. Tests must be performed and/or it has to be proven that the component in question functions properly resulting in a considerable delay before new types of components can be used in safety-related applications.